Aggressive personality 'doubles stroke risk'

The Daily Mail informed us today that aggressive behaviour ‘doubles risk of stroke’ and that ‘being aggressive, quick tempered and impatient can increase the risk of stroke as much as smoking’.

This headline conjures up the old saying to ‘burst a blood vessel’ when angry, and is based on a small study that compared people admitted to hospital with a stroke with healthy people.

Researchers aimed to investigate whether particular behaviours such as feeling stressed or depressed and a ‘type A personality’ increased the risk of stroke in a population aged below 65 years living in Madrid.

A type A personality have been described as being aggressive, highly strung, organised and competitive.

They found that people reporting higher scores on a stress scale and type A personality checklist were slightly more than twice as likely to have a stroke than their ‘non-stressed’ counterparts.

However, this study provided little evidence to suggest that aggressive behaviour increases the risk of stroke as there were significant limitations. This included that the majority of people who took part in the study were urban-dwelling Spanish people under the age of 65 – so the result may not translate to other groups.

Also the study is prone to what is known as recall bias – that is people recovering from a stroke are arguably more likely to think that feelings of stress contributed to their ill health than healthy people (who may also be stressed but tend to not to dwell on it).

While a link between stress and stroke is plausible, this study alone does not provide firm evidence that stress causes stroke.

Where did the story come from?

The study was carried out by researchers from various Spanish Universities and other institutions. It was funded by the Spanish Health Research Foundation within the European Regional Development Fund. The study was published in the peer-reviewed Journal of Neurology, Neurosurgery and Psychiatry.

Despite the exaggerated headlines, the story itself is covered appropriately by the Mail.

What kind of research was this?

This was a case-control study which looked at the link between reported ‘psychosocial stress’ (chronic stress) and risk of having a stroke in people younger than 65 years living in Madrid, Spain.

A case-control study compares people who have a condition of interest (cases) with those who do not (controls). The past histories and characteristics of the two groups are examined to see how they differ. This type of study is often used to identify risk factors for rare medical conditions.

Arguably, as stroke is fairly common, a more useful study design would have been a cohort study which assessed the characteristics of a large group of people and then followed them over time to examine how factors such as stress impacted on their health outcomes.

Being a case control where the ‘cases’ already had a stroke, this study is limited by the fact that it only included a select population of people with stroke. It had to exclude people with more severe stroke and resulting speech and language problems who could not take part.

A cohort study that assessed people prior to stroke would be able to include people with all types of stroke, and would also decrease the possibility of biased reporting on stress (recall bias) by people who have already had a stroke.

What did the research involve?

The researchers recruited 150 patients aged between 18 and 65 years that were admitted on a consecutive basis to a Stroke Unit in Madrid with a diagnosis of stroke (considered as cases).

The cases’ ability to answer study questions was assessed and if they were unable to, answers from a family member or carer were sought (although these patients were excluded in the main analysis).

For the control group, 300 people were randomly selected from the same district in Madrid and any that had a previous stroke were excluded. Cases who were able to then completed questionnaires during interviews in the week following the stroke. Controls were assessed by face-to-face interviews.

To determine each participant’s psychophysical (chronic) stress, scores were combined from different questionnaires that assessed:

general wellbeing

quality of life

symptoms such as anxiety, depression and stressful symptoms in the previous year.

Behaviour patterns were also assessed by questionnaire with total scores varying between 8 and 35, and a score of 24 or higher indicating a pattern of type A behaviour. Other risk factors for stroke were also assessed including:

diabetes

high blood pressure or history of heart problems

high cholesterol

tobacco, alcohol and energy drink intake

Characteristic details such as age, gender, education level, sleep disorders and whether the participant had a job, partner or children, were also taken into consideration and appropriate statistical analysis was carried out.

What were the basic results?

The average age of participants was 53.8 for cases and 53.6 for controls. Following adjustment for confounders the main findings from this study were:

on a questionnaire of life events, people who reported more stressful experiences in the previous year (with a score suggesting that they were at ‘intermediate risk’ of having an illness in the near future) had an increased risk of stroke compared to controls (odds ratio 3.84, 95% confidence interval 1.91 to 7.70)

people who had behavioural patterns indicating a type A personality were considered to have an increased likelihood of having a stroke compared to controls (odds ratio 2.23, 95% confidence interval 1.19 to 4.18)

Other factors that were also independently associated with increased risk of stroke were:

male gender

consumption of energy drinks more than twice a day

being a current or ex-smoker

having heart rhythm problems

poor quality of night-time sleep

No significant differences were seen for other measures of general health.

How did the researchers interpret the results?

The researchers conclude that, compared to healthy individuals, stressful habits and ‘type A behaviour’ are associated with a high risk of stroke. The effect of these stresses was comparable in men and women.

In discussing the study findings, lead researcher Dr Jose Antonio Egido said ‘patterns of behaviour can reflect the capacity to adapt to a stressful life’. He added that addressing the influence of psychosocial factors such as stress on stroke could help to prevent stroke in people considered to be at-risk and ‘warrants further investigation’.

Conclusion

Overall, this study provides little evidence that aggressive behaviour ‘increases risk of stroke’. There are some important limitations to this study, primarily due to the case-control study design:

Approximately 40% of potentially eligible participants had to be excluded from the study as they had extensive stroke. Mostly this was because the stroke had impaired their speech and language to such a degree that they were unable to participate in the questionnaires. This is important as findings from this study do not relate to this more severe stroke population.

The study only looked at participants who were between the ages of 18 and 65 years, so findings cannot be generalised to age groups outside of this range. This is important as the risk for stroke increases with age and you are more likely to have a stroke if you are over 65 years.

It is possible that people did not accurately report their behavioural patterns. As some of the risk factors were assessed by self-report, this may make the results less reliable than objective measures. Particularly as assessments were carried out after the ‘cases’ had already had a stroke. This further increases the chance of recall bias. It is possible that people who had already had a stroke felt more inclined to report feeling stressed in the year leading up to their stroke.

Despite the authors efforts to adjust their results for confounders it is always possible that other factors influenced the results.

High stress has often been linked to increased risk of high blood pressure and cardiovascular disease, so the link is plausible, but overall the headline in the Daily Mail is not supported by these research findings alone.

Further research, ideally involving a larger cross-section of the population and carried out on a cohort study basis, would possibly provide a more accurate picture of how emotions such as stress and aggression contribute towards stroke risk.

The best known way to reduce risk of stroke is to eat a healthy, balanced diet, take regular exercise and avoid smoking and excess alcohol.